powerpc: EX_TABLE macro for exception tables

This macro is taken from s390, and allows more flexibility in
changing exception table format.

mpe: Put it in ppc_asm.h and only define one version using
stringinfy_in_c(). Add some empty definitions and headers to keep the
selftests happy.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/copyloops/asm/ppc_asm.h

@@ -25,6 +25,8 @@
 
 #define PPC_MTOCRF(A, B)	mtocrf A, B
 
+#define EX_TABLE(x, y)
+
 FUNC_START(enter_vmx_usercopy)
 	li	r3,1
 	blr

tools/testing/selftests/powerpc/primitives/asm/ppc_asm.h

@@ -0,0 +1 @@
+../../../../../../arch/powerpc/include/asm/ppc_asm.h